Issuance
Receives one offer's credentials: show offer; then beginAuthorization, open the URL in an Auth Tab or Custom Tab and completeAuthorization, or redeemPreAuthorizedCode; then requestCredentials; close when done. An issuance dropped without close leaves its keys until Wallet.sweepOrphanedKeys.
Types
An offered credential that couldn't be obtained: its error's code and, when the issuer gave one, its OAuth error code.
What Issuance.requestCredentials obtained.
Functions
Begins the authorization code grant, returning the issuer's authorization URL to open in an Auth Tab or Custom Tab. Calling it again begins again: after the holder closed the page, say.
Completes the authorization with the issuer's redirect back. The redirect is used up whatever happens: if this fails — the token request didn't get through, say — call beginAuthorization again, rather than retrying this.
Redeems a pre-authorized code offer, with the PIN the holder typed when Offer.txCode asks for one. A wrong PIN throws a retryable protocol error (invalid_grant): ask again.
Requests, checks and stores every offered credential.